Multi-layered composite filter media and pleated filter element constructed therefrom

ABSTRACT

A multi-layered pleated filter element for filtering drinking water is disclosed which includes at least one upstream glass fiber layer for pre-filtration, a nanofiber membrane layer for bacteria retention, and at least one downstream positively charged microporous membrane layer for virus retention.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 62/121,605, filed Feb. 27, 2015, which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention is directed to fluid filtration, and more particularly, to a multi-layered composite filter media for filtering drinking water, a pleated filter element formed from the composite filter media, a filter cartridge containing the pleated filter element, a counter top dispenser utilizing the filter cartridge and a portable bottle utilizing the filter cartridge.

2. Description of Related Art

Drinking water in many areas of the world contains dissolved chemicals and suspended particulate material, as a consequence of run-off and environmental contamination. Some of these chemicals and particulates have been associated with adverse physiological effects. Others have been associated with less than desirable taste and sensory perceptions.

To reduce particulate and chemical contamination, drinking water is frequently treated by chemical processes. However, these processes may introduce other types of undesirable chemical contaminants into the water. Chemicals, such as bromine and chlorine, are also frequently added to water to act as a sanitizing agent. The dangers associated with these chemicals have been questioned.

There is a general view that municipal water treatment plants often fail to adequately deal with these problems. To improve water quality, many residences and businesses now employ on-site water filters to improve water streams consumed therein.

Most systems for improving water quality use a series of filters. Filtration is the process of separating particles from a fluid suspension by use of a porous medium or by means of a medium possessing chemical properties, such as hydrophobicity, electrostatic charge, etc., which permit the medium to interact with and hold the particles to be separated from the fluid, while permitting the fluid to pass there through.

Chemical contaminants are often removed by filters through chemical absorption into, or adsorption onto, the surface of the filter medium. Optimally, it is desired that the filter medium retains most of the suspended particles and many of the chemical contaminants, but allows the fluid being filtered to pass through unimpeded. Flow across the filter medium is generally achieved by the application of a driving force, usually in the form of a pressure difference across the filter, which may be generated by external pressure applied upstream, a vacuum applied downstream, gravity, or another force.

Fluid filters are often constructed in the form of relatively rigid replaceable filter units or “filter cartridges.” Filter cartridges often employ granular activated carbon elements in their construct. Granular activated carbon is useful for removing organic chemicals such as chlorine, hydrogen sulfide, pesticides, herbicides, phenol, chlorophenol and hydrocarbon from water. Other filter elements may be employed in the cartridge construct to help, for example, to remove sediments such as rust and other particles. Silver is sometimes impregnated into one or more filter element to inhibit bacterial growth. Ion exchange resins may also be employed.

While filter cartridges containing granular activated carbon are known to be good at removing contaminants that affect taste, odor of the filtrate, and visible particulate matter, such filter cartridges generally are not fine enough to remove bacteria or viruses. Water may be contaminated with a number of micro-organisms including pathogenic bacteria, amoebae, flagellates, viruses and protozoa. In fact, as some water remains inside carbon granules after filtration, stagnant water in the carbon granules may act as a breeding ground for micro-organisms. Therefore, water discharged after a long period of non-use of a carbon-based filter cartridge may be contaminated with living organisms.

Recognizing that prior art filter cartridges which incorporate only a single filter medium, in particular a carbonaceous medium, suffer from the inability to remove many of the contaminants found in water, there have been developed filter assemblies employing a plurality of filter media. For example, filter assemblies have been developed that include an outer cylindrical filter structure with porosity to remove particulate matter, an inner cylindrical sorbent structure for sorbing chemical contaminants, and an inner-most cylindrical microbiological filter, preferably comprising a microporous membrane or a microporous fiber bundle for removing microorganisms. By moving water through the assembly, from the outer structure to the inner structure, particulates are removed, chemicals are adsorbed or absorbed, and microorganisms are filtered out.

Many on-site water filters are designed to be mounted in a permanent housing coupled to a water stream. These permanent housings are often located in relatively poorly accessible locations, such as under a sink or in the basement of a home, and often require special tools in order to gain access to the filter residing in the housing. While on-site permanent filters are often perceived to remediate the water sufficiently for everyday use, there is a growing number of people who demand cleaner and more tasteful water for consumption.

Rather than adding new types of filters into permanent-type on-site water filter housings or increasing the number of such housings, to provide for a more convenient manner of coupling filters to water streams and of changing filters, so-called “countertop filtration units” have been developed. Countertop filtration units are portable filter devices dimensioned to fit on a standard household countertop and adapted for coupling to a fluid flow outlet, such as a faucet. They may also be designed as gravity fed devices. They are also common and useful in developing nations and other situations where people are living off the electrical grid, because they require no power.

Filters used in countertop filtration units are designed to be disposable. One commonplace type of disposable filter is in the form of a solid porous cylinder having a hollow center. When such filters are employed, the fluid to be filtered flows radially through the wall of the cylinder, between its exterior and hollow core. Such filters are generally capped at each end with a boundary sealing cap to permit sealing between the filter and its housing to ensure that only fluid having passed through the wall of the filter cylinder and into the hollow core is permitted to exit from the filtration unit.

Typically, countertop filtration units employ filters fabricated from granular activated carbon. As noted above, while carbonaceous filter elements are known to be good at removing contaminants that affect taste, odor of the filtrate, and visible particulate matter, such filters generally are not fine enough to remove bacteria or viruses.

Accordingly, there is a need in the art for a gravity fed countertop filtration unit with a removable and replaceable filter cartridge that includes filter media configured to remove bacteria and viruses from drinking water. There is also a need in the art for a portable gravity fed water bottle with a replaceable filter cartridge adapted to remove contaminants and particulate matter, as well as, bacteria and, optionally, viruses from drinking water.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful multi-layered composite filter media for drinking water that is adapted and configured to remove contaminants that affect the taste and odor of the water, as well as visible particulate matter, and micro-organisms such as bacteria and viruses. The filter media includes at least one pre-filtration layer, a bacteria retention layer, and at least one virus retention layer.

Preferably, the at least one pre-filtration layer is a glass fiber pre-filtration layer, the bacteria retention layer is a nanofiber membrane layer, and the at least one virus retention layer is a positively charged microporous media layer that includes a porous substrate with a cross-linked polymer coating. The media can be a non-woven material. The porous substrate is preferably made of glass fiber or a similar material.

The nanofiber membrane layer is preferably formed of an electrospun polymer resin. The electrospun polymer resin is preferably Polyacrylonitrile (PAN) or a similar material. For example, the resin could be any polymeric material which is soluble in solvents suitable for electrospining, such as PolyEther Sulfone (PES), Nylon or Poly Vinylidene Di Fluoride (PVDF). The nanofiber membrane layer includes a substrate made of polyethylene terephthalate (PET) or a similar material. The nanofiber membrane layer has an average thickness of about between 170 to 210 μm. Preferably, the nanofiber membrane has a thickness of about between 30 and 60 μm and the substrate has an average thickness of about between 140 to 150 μm.

The subject invention is also directed to a new and useful multi-layered pleated filter element that includes at least one upstream glass fiber layer for pre-filtration, an interior nanofiber membrane layer for bacteria retention, and at least one downstream positively charged microporous media layer for virus-retention. Preferably, the pleated filter element includes, among other things, first and second glass fiber layers for pre-filtration, and first, second positively charged microporous media layers for virus retention. A third positively charged microporous media layers may also be provided.

The subject invention is also directed to a new and useful filter cartridge that includes a housing having an inlet region for the ingress of an unfiltered fluid and an outlet region for the egress of filtered fluid, and a multi-layered pleated filter element disposed within the housing. The multi-layered pleated filter element of the filter cartridge includes at least one upstream layer for pre-filtration, a nanofiber membrane layer for bacteria retention, and at least one downstream positively charged microporous media layer for virus-retention.

Preferably, the pleated filter element within the cartridge housing is a radially pleated filter element with an outer periphery and an inner periphery, wherein the upstream pre-filtration layer is positioned at the inner periphery of the pleated filter element and the downstream virus retention layer is positioned at the outer periphery of the pleated filter element. Preferably, the housing includes a cover portion having the inlet region, and the inlet region is in fluid communication with the inner periphery of the filter element. The outlet region includes a plurality of circumferentially spaced apart outlet ports formed about an upper peripheral edge of the housing. Preferably, the pleated filter element is potted on an interior surface of the cover portion.

The subject invention is also directed to a new and useful counter top dispenser for filtering drinking water through a gravity fed process that includes an upper basin for receiving unfiltered water, a lower basin connected to the upper basin for storing filtered water, wherein the a tap is provided for accessing the filtered water. In one embodiment of the subject invention, a prefilter is located within the upper basin for removing large particles and contaminants from the water, and a pleated purification cartridge is located within the lower basin and connected in series with the prefilter for removing bacteria and viruses from the prefiltered water. In another embodiment of the subject invention, the filter cartridge is operatively associated with the either the upper basin or the lower basin, and it performs prefiltration of particulates as well as filtration of bacteria and viruses.

The subject invention is also directed to a new and useful portable bottle for filtering drinking water which includes, among other things, a bottle having a threaded opening, a cap for threadably cooperating with the opening of the bottle, a spout operatively associated with the cap, and a replaceable filter cartridge assembly for mating with the cap. Preferably, the filter cartridge assembly includes a multi-layered pleated filter element having at least one pre-filtration layer, a bacteria retention layer made of an electrospun nanofiber membrane, and a carbon block core disposed within an inner peripheral region of the pleated filter element.

These and other features of the multi-layered composite filter media of the subject invention and the manner in which it is manufactured and employed in cartridges and the like will become more readily apparent to those having ordinary skill in the art from the following enabling description of the preferred embodiments of the subject invention taken in conjunction with the several drawings described below.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the multi-layered composite filter media of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

FIG. 1 is a photograph of a sector of a multi-layered pleated composite filter media constructed in accordance with a preferred embodiment of the subject invention;

FIG. 2 is an SEM image at approximately 5700× magnification of an electro-spun nanofiber bacteria retention membrane, which forms part of the composite filter media of the subject invention;

FIG. 3 is a perspective view of a radially pleated filter element constructed in accordance with a preferred embodiment of the subject invention, with parts separated for ease of illustration;

FIG. 4 is an illustration of a filter cartridge constructed in accordance with a preferred embodiment of the subject invention, which contains a pleated filter element as shown in FIG. 3;

FIG. 5 is an illustration of a counter top water dispenser that includes the filter cartridge shown in FIG. 4; and

FIG. 6 is an exploded perspective view of a portable drinking bottle constructed in accordance with a preferred embodiment of the subject invention, which includes a replaceable filter cartridge element containing the multi-layered pleated composite filter media depicted in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals identify similar structural features or aspects of the subject invention, there is illustrated in FIG. 1 a multi-layered pleated composite filter media constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral 10. The multi-layered pleated composite filter media 10 of the subject invention is particularly well-suited for filtering drinking water. More particularly, the composite media is configured to remove contaminants as well as visible particulate matter such as dust, silt cysts and sand, in addition to micro-organisms such as bacteria and viruses.

Referring to FIG. 1, in an exemplary embodiment of the invention, the composite filter media 10 includes two upstream pre-filtration layers 12, an interior bacteria retention layer 14, and three downstream virus retention layers 16. Those skilled in the art will readily appreciate that the number of layers and their relative positions within the composite structure could vary depending upon application. The pre-filtration layers 12 are preferably made from glass fiber and are configured to remove relatively large particulates from the fluid being filtered.

The bacteria retention layer 14 is a three-dimensional nanofiber membrane layer. More particularly, as illustrated in FIG. 2, the nanofiber membrane layer 14 is formed of an electrospun polymer resin. A prior art filter media having an electro spun nanofiber filter media is disclosed for example in U.S. Pat. No. 8,172,092, the disclosure of which is incorporated herein by reference in its entirety. The polymer resin from which the nanofiber membrane layer 14 of the subject invention is made is Polyacrylonitrile (PAN) or a similar material. PAN is a synthetic, semi crystalline organic polymer resin, with the linear formula (C₃H₃N)_(n). Though it is thermoplastic, it does not melt under normal conditions. It degrades before melting. It melts above 300° C. if the heating rates are 50 degrees per minute or above. Almost all polyacrylonitrile resins are copolymers made from mixtures of monomers with acrylonitrile as the main component.

The nanofiber membrane layer 14 is designed to achieve a relatively high flow rate and includes a substrate made of polyethylene terephthalate (PET) or a similar polymeric substrate material. The nanofiber membrane layer has an average thickness of about between 170 to 210 μm. Preferably, the nanofiber membrane itself has a thickness of about between 30 and 60 μm and the substrate portion of the layer 14 has an average thickness of about 140 to 150 μm.

Referring back to FIG. 1, the virus retention layers 16 are all positively charged microporous media layers that include a porous substrate with a cross-linked polymer coating. A prior art microporous membrane is disclosed for example in U.S. Pat. No. 7,396,465, the disclosure of which is incorporated by reference herein in its entirety. The porous substrate portion of the virus retention layer is preferably made of glass fiber or a similar material.

Referring now to FIG. 3, there is illustrated a perspective view of a pleated filter element constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral 20. The pleated filter element 20 includes the composite media 10 shown in FIG. 1, in a radially pleated format. The pleated filter element 20 includes an upper or top end cap 22, an optional lower or bottom end cap 24 and an optional perforated core 26. As shown in FIG. 3, the radially pleated filter element 20 is defined by an outer diameter (1), a lengthwise height (2) and an inner diameter (3). It is envisioned that the filter element 20 could be potted into the upper end cap 22, the lower end cap 24 or it could be potted into both the upper and lower end caps.

Referring now to FIG. 4, there is illustrated a replaceable and disposable filter cartridge constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral 30. Filter cartridge 30 is particularly adapted for use in a gravity-fed water filtration system. It has a generally cylindrical housing 32 that includes a cover portion 34 having an inlet region defined by an inlet 35, and an outlet region defined by a plurality of circumferentially spaced apart outlet ports 36 formed about an upper peripheral edge of the housing 32. Inlet 35 can be threaded as shown or it could have a different mechanical fitting such as, for example, a bayonet type coupling.

Referring now to FIG. 5, there is illustrated a counter top dispenser for filtering drinking water that is constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral 40. The dispenser 40 includes an upper basin 42 for receiving unfiltered water, a lower basin 44 connected to the upper basin 42 for storing filtered water and including a tap 45 for accessing the filtered water.

In one embodiment of the subject invention, a prefilter 46 is located within the upper basin 42 for removing large particles and contaminants such as organic compounds from the water, and a purification cartridge 48 is located within the lower basin 44 and connected in series with the prefilter 46 for removing bacteria and viruses from the prefiltered water. The prefilter preferably includes a carbon block element. In another embodiment of the subject invention, the filter cartridge 30 is operatively associated with the either the upper basin 42 or the lower basin 44, and it performs prefiltration of particulates as well as filtration of bacteria and viruses.

Referring to FIG. 6, there is illustrated a portable bottle for filtering drinking water that is constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral 50. The portable bottle 50 includes a thermoplastic bottle portion 52 having a threaded opening, a cap 54 for threadably cooperating with the opening of the bottle portion 52, a spout 56 operatively associated with the cap 54, and a replaceable filter cartridge assembly 58 for mating with the cap 54. The filter cartridge assembly 58 includes a multi-layered pleated filter element 60 having at least one pre-filtration layer, a bacteria retention layer made of an electrospun nanofiber membrane, and a carbon block core 62 disposed within an inner peripheral region of the pleated filter element 60. A tethered cover 64 is also provided for cooperating with the spout 56.

While the subject invention has been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention as defined by the appended claims. 

What is claimed is:
 1. A multi-layered composite filter media comprising: a) at least one pre-filtration layer; b) a bacteria retention layer; and c) at least one virus retention layer.
 2. A multi-layered composite filter media as recited in claim 1, wherein the at least one pre-filtration layer is a glass fiber pre-filtration layer.
 3. A multi-layered composite filter media as recited in claim 1, wherein the bacteria retention layer is a nanofiber membrane layer.
 4. A multi-layered composite filter media as recited in claim 3, wherein the nanofiber membrane layer is formed of an electrospun polymer resin.
 5. A multi-layered composite filter media as recited in claim 3, wherein the electrospun polymer resin is Polyacrylonitrile (PAN).
 6. A multi-layered composite filter media as recited in claim 3, wherein the nanofiber membrane layer includes a substrate made of polyethylene terephthalate (PET).
 7. A multi-layered composite filter media as recited in claim 6, wherein the nanofiber membrane layer has an average thickness of about between 170 to 210 μm.
 8. A multi-layered composite filter media as recited in claim 7, wherein the nanofiber membrane has a thickness of about between 30 and 60 μm and the substrate has an average thickness of about between 140 to 150 μm.
 9. A multi-layered composite filter media as recited in claim 1, wherein the at least one virus retention layer is a positively charged microporous media layer.
 10. A multi-layered composite filter media as recited in claim 9, wherein the positively charged microporous media layer includes a porous substrate with a cross-linked polymer coating.
 11. A multi-layered composite filter media as recited in claim 10, wherein the porous substrate of the at least one virus retention layer is made of glass fiber.
 12. A multi-layered pleated filter element comprising: a) at least one upstream glass fiber layer for pre-filtration; b) an interior nanofiber membrane layer for bacteria retention; and c) at least one downstream positively charged microporous media layer for virus retention.
 13. A multi-layered pleated filter element as recited in claim 12, wherein the nanofiber membrane layer is formed of an electrospun polymer resin.
 14. A multi-layered pleated filter element as recited in claim 13, wherein the electrospun polymer resin is Polyacrylonitrile (PAN).
 15. A multi-layered pleated filter element as recited in claim 13, wherein the nanofiber membrane layer includes a substrate made of polyethylene terephthalate (PET).
 16. A multi-layered pleated filter element as recited in claim 13, wherein the at least one positively charged microporous media layer includes a porous substrate with a cross-linked polymer coating.
 17. A multi-layered pleated filter element as recited in claim 16, wherein the porous substrate of the at least one virus retention layer is made of glass fiber.
 18. A multi-layered pleated filter element as recited in claim 12, including first and second glass fiber layers for pre-filtration.
 19. A multi-layered pleated filter element as recited in claim 12, including first, second and third positively charged microporous media layers for virus retention.
 20. A filter cartridge comprising: a) a housing having an inlet region for the ingress of an unfiltered fluid and an outlet region for the egress of filtered fluid; and b) a multi-layered pleated filter element disposed within the housing and including: i) at least one upstream layer for pre-filtration; ii) an interior nanofiber membrane layer for bacteria retention; and iii) at least one downstream positively charged microporous media layer for virus retention.
 21. A filter cartridge as recited in claim 20, wherein the pleated filter element is a radially pleated filter element with an outer periphery and an inner periphery.
 22. A filter cartridge as recited in Clam 21, wherein the upstream pre-filtration layer is positioned at the inner periphery of the pleated filter element.
 23. A filter cartridge as recited in Clam 21, wherein the downstream virus retention layer is positioned at the outer periphery of the pleated filter element.
 24. A filter cartridge as recited in claim 20, wherein the housing includes a cover portion having the inlet region, and wherein the inlet region is in fluid communication with the inner periphery of the filter element.
 25. A filter cartridge as recited in claim 20, wherein the pleated filter element is potted on an interior surface of the cover portion.
 26. A filter cartridge as recited in claim 20, including first and second glass fiber layers for pre-filtration.
 27. A filter cartridge as recited in claim 20, including first, second and third positively charged microporous media layers for virus retention.
 28. A filter cartridge as recited in claim 20, wherein the outlet region includes a plurality of circumferentially spaced apart outlet ports formed about an upper peripheral edge of the housing. 